수리 사례

2026. 6. 30. 작업

증상

Why aren’t drive chains completely taut?

처리 내용

The main reason slack is needed is the rear suspension of the bike. In a "perfect" setup, the axis of the rear swing-arm and the final drive of the engine would be one and the same. This is not normally possible so a compromise must be made. In this diagram, you can see the two different axis. Because of this, on a typical street bike, the chain has more tension when you are sitting on the bike and the rear suspension is slightly compressed. A common mistake is to make the chain tight when it's on a stand and then ending up with a chain that is way too tight once you're riding. Chain and suspension geometry is a pretty complex topic. The diagram above is from this site which also has a lot more technical information. https://www.sportrider.com/more-fun-geometry#page-3 Another reason for the slack is the physics problem of why you can never pull a rope across two points to make it perfectly straight . Gravity is going to make the chain sag and appear to have some slack. The amount of fo